Synthesis and Characterization of Dinaphtho[2,1-<i>a</i>:2,3-<i>f</i>]pentalene: A Stable Antiaromatic/Quinoidal Hydrocarbon Showing Appropriate Carrier Mobility in the Amorphous Layer

Horii, Koki; Nogata, Akira; Mizuno, Yusuke; Iwasa, Haruna; Suzuki, Mitsuharu; Nakayama, Keiichi I.; Konishi, Akihito; Yasuda, Makoto

doi:10.1246/cl.210809

Cited by 7 publications

(15 citation statements)

References 48 publications

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“…28 Although sulfur-embedded small polycyclic aromatic system was reported to show good SCLC hole mobility (8.72 × 10 −2 cm 2 · V −1 · s −1 ), 25a hydrocarbon motifs like antiaromatic diareno-pentalene showed low hole-carrier mobility (4.37 × 10 −4 cm 2 · V −1 · s −1 ) under the SCLC method. 29 Considering [2,1- c ]IF as a benzo-interpositioned 30 pentalene system, our studies on the symmetrical or unsymmetrical [2,1- c ]IFs 1 , 7 , 8 and 17 π-systems revealed an order of magnitude greater charge-carrier mobility for both holes and electrons. Moreover, a balanced ambipolar charge-transport behavior could be extracted for the first time.…”

Section: Resultsmentioning

confidence: 86%

“…Mp: 55 -56 °C. 1 H NMR (400 MHz, CDCl 3 ): δ 9.92 -9.86 (m, 1 H), 8.17 (29). Under a nitrogen atmosphere, in 10 mL dry THF solution of 27 (162 mg, 0.43 mmol), (3,5-bis(trifluoromethyl)phenyl)magnesium bromide (prepared from 1-bromo-3,5-bis(trifluoromethyl)benzene (0.37 mL, 2.15 mmol) and magnesium turning (63 mg, 2.58 mmol) in dry THF (5 mL)) was added dropwise.…”

Section: Methodsmentioning

confidence: 99%

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Exploring Indeno[2,1-c]fluorene Antiaromatics with Unsymmetrical Disubstitution and Balanced Ambipolar Charge-Transport Properties

et al. 2023

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Unsymmetrically disubstituted antiaromatic indenofluorene (IF), in comparison to aromatic pentacene counterpart with unsymmetrical disubstitution, was rare in literature until our recent report on indeno[1,2-b]fluorene and indeno[2,1-a]fluorene. Described herein is straightforward access to unsymmetrically disubstituted indeno[2,1-c]fluorenes bearing mesityl at one apical carbon and C6F5, 3,5-(CF3)2C6H3, and CCSii-Pr3 at the other apical carbon, including 4-methoxyphenyl/3,5-(CF3)2C6H3 push/pull substitution at the apical carbons with appreciable orbital density and a previously unknown symmetrically C6F5-disubstituted [2,1-c]IF. The electronic properties of the unsymmetrical derivatives lie halfway in between the two symmetrical counterparts, while the 4-methoxyphenyl derivative showed the smallest HOMO-LUMO energy gap and near-infrared absorption with intramolecular charge transfer character. Single-crystal analyses showed 1D-columnar stacks for the unsymmetrical motif with the C6F5 units co-facially π-stacked with the IF core, whereas symmetrically C6F5-disubstituted [2,1-c]IF, with a low-lying LUMO, showed intermolecular π-π stacks between the IFs core that resulted in good electron mobility (μe = 8.66 × 10−3 cm2 V−1 s−1) under space charge limited current measurements. Importantly, balanced ambipolar charge-transport behaviour could be extracted for an IF series with symmetrical/unsymmetrical substitutions, in comparison to its π-contracted pentalene congener.

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Section: Resultsmentioning

confidence: 86%

Section: Methodsmentioning

confidence: 99%

Exploring Indeno[2,1-c]fluorene Antiaromatics with Unsymmetrical Disubstitution and Balanced Ambipolar Charge-Transport Properties

et al. 2023

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“…It is of substantial interest to utilize s -indacene derivatives as organic semiconductors in solution-processed OFET devices with an aim to unveil the relationships among molecular structure, solid state packing, and charge transport properties of antiaromatic compounds. The congeners of DBP and [1,2- b ]IF that have been employed for OFETs are regarded as pentalene- and s -indacene-based materials, respectively. − Nevertheless, up to now, an intrinsic tricyclic s -indacene derivative has never been evaluated in OFETs. Here we selected hexaxylyl derivative 1f which is endowed with stability and solution processability for a preliminary OFET application.…”

Section: Resultsmentioning

confidence: 99%

“…The concept of antiaromaticity was established many decades ago for prototypical monocyclic hydrocarbons of 4 n π-electrons. , However, polycyclic antiaromatic hydrocarbons (PAAHs) have attracted renewed interest during the last two decades in view of new criteria of antiaromaticity − and small energy gaps between HOMO/LUMO levels and the Fermi level, which are relevant to open-shell character , and carrier mobility in organic field-effect transistors (OFETs). − Among PAAHs, dibenzo[ a , e ]pentalene (DBP) and indeno[1,2- b ]fluorene ([1,2- b ]IF) (Figure a), which belong to nonalternant hydrocarbons bearing five-membered rings, have been intensively investigated as stable singlet diradicals − and building blocks ,− for conjugated polymers and macrocyclic molecules of unique topology and for optoelectronic applications. − These are environmentally stable due to benzo fusion to 8 π-electron pentalene − and 12 π-electron s -indacene ( 1a ), , respectively, which are highly reactive without steric protection. − However, PAAHs without benzo fusion have never been exploited for systematic study of their structure and physical properties and, needless to say, for materials applications. We envisioned that hexaaryl derivatives of s -indacene ( 1a ) would be stable enough for such purposes in view of the weak antiaromaticity − and moderate open-shell character ,, theoretically predicted for 1a .…”

Section: Introductionmentioning

confidence: 99%

s-Indacene Revisited: Modular Synthesis and Modulation of Structures and Molecular Orbitals of Hexaaryl Derivatives

et al. 2023

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Though s-indacene is an intriguing antiaromatic hydrocarbon of 12 π-electrons, it has been underrepresented due to the lack of efficient and versatile methods to prepare stable derivatives. Herein we report a concise and modular synthetic method for hexaaryl-s-indacene derivatives bearing electron-donating/-accepting groups at specific positions to furnish C 2h -, D 2h -, and C 2v -symmetric substitution patterns. We also report the effects of substituents on their molecular structures, frontier molecular orbital (MO) levels, and magnetically induced ring current tropicities. Both theoretical calculations and X-ray structure analyses indicate that the derivatives of the C 2h -substitution pattern adopt different C 2h structures with significant bond length alternation depending on the electronic property of the substituents. Due to the nonuniform distribution of the frontier MOs, their energy levels are selectively modulated by the electron-donating substituents. This leads to the inversion of the HOMO and HOMO–1 sequences with respect to those of the intrinsic s-indacene as theoretically predicted and experimentally proven by the absorption spectra at visible and near-infrared regions. The NICS values and the 1H NMR chemical shifts of the s-indacene derivatives indicate their weak antiaromaticity. The different tropicities are explained by the modulation of the HOMO and HOMO–1 levels. In addition, for the hexaxylyl derivative, weak fluorescence from the S2 excited state was detected due to the large energy gap between the S1 and S2 states. Notably, an organic field-effect transistor (OFET) fabricated using the hexaxylyl derivative exhibited moderate hole carrier mobility, a result which opens the door for optoelectronic applications of s-indacene derivatives.

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“…16,50,51 From this perspective, we have recently focused on diareno[a,f ]pentalenes 52−54 and disclosed the interrelation between their antiaromatic and open-shell characteristics, 55,56 showing hole transport behavior. 57 In a series of diareno[a,f ]pentalenes 1−5 (Figure 2A), the following two principles that govern the interrelation between the antiaromatic and open-shell characteristics are derived: (1) the mode of the embedded o-quinoidal moiety and (2) the formal molecular symmetry of the ring fusion pattern. The open-shell and closed-shell singlet ground states are attained by the attachment of the o-benzoquinoidal and 1,2-naphthoquinoidal moieties to the pentalene skeleton, respectively.…”

Section: ■ Introductionmentioning

confidence: 99%

Synthesis and Characterization of Dibenzothieno[a,f]pentalenes Enabling Large Antiaromaticity and Moderate Open-Shell Character through a Small Energy Barrier for Bond-Shift Valence Tautomerization

Mizuno,

Nogata,

Suzuki

et al. 2023

J. Am. Chem. Soc.

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Experimental and theoretical rationalization of bond-shift valence tautomerization, characterized by double-well potential surfaces, is one of the most challenging topics of study among the rich electronic properties of antiaromatic molecules. Although the pseudo-Jahn–Teller effect (PJTE) is an essential effect to provide attractive characteristics of 4nπ systems, an understanding of the structure–property relationship derived from the PJTE for planar 4nπ electron systems is still in its infancy. Herein, we describe the synthesis and characterization of two regioisomers of the thiophene-fused diareno[a,f]pentalenes 6 and 7. The magnetic and optoelectronic properties characterize these sulfur-doped diareno[a,f]pentalenes as open-shell antiaromatic molecules, in sharp contrast to the closed-shell antiaromatic systems of 3 and 5, in which these main cores consist of the same number of π electrons as 6 and 7. Notably, thiophene-fused 6b and 7b showed pronounced antiaromaticity, the strongest among the previous systems, as well as moderate open-shell characteristics. Our experimental and theoretical investigations concluded that these properties of 6b and 7b are derived from the small energy barrier E a ‡ for the bond-shift valence tautomerization. The energy profile of the single crystal of 6b showed the temperature-dependent structural variations assigned to the dynamic mutual exchange between the two C s -symmetric structures, which was also supported by changes in the chemical shifts of variable-temperature 1H NMR spectra in the solution phase. Both experimental and computational results revealed the importance of introducing heteroaromatic rings into 4nπ systems for controlling the PJTE and manifesting the antiaromatic and open-shell natures originating from the high-symmetric structure. The findings of this study advance the understanding of antiaromaticity characterized by the PJTE by controlling the energy barrier for bond-shift valence tautomerizations, potentially leading to the rational design of optoelectronic devices based on novel antiaromatic molecules possessing the strong contributions of their high-symmetric geometries.

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Synthesis and Characterization of Dinaphtho[2,1-a:2,3-f]pentalene: A Stable Antiaromatic/Quinoidal Hydrocarbon Showing Appropriate Carrier Mobility in the Amorphous Layer

Cited by 7 publications

References 48 publications

Exploring Indeno[2,1-c]fluorene Antiaromatics with Unsymmetrical Disubstitution and Balanced Ambipolar Charge-Transport Properties

Exploring Indeno[2,1-c]fluorene Antiaromatics with Unsymmetrical Disubstitution and Balanced Ambipolar Charge-Transport Properties

s-Indacene Revisited: Modular Synthesis and Modulation of Structures and Molecular Orbitals of Hexaaryl Derivatives

Synthesis and Characterization of Dibenzothieno[a,f]pentalenes Enabling Large Antiaromaticity and Moderate Open-Shell Character through a Small Energy Barrier for Bond-Shift Valence Tautomerization

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